Post‐transcriptional regulation of Ghd7 protein stability by phytochrome and Os GI in photoperiodic control of flowering in rice

• Published in: The New phytologist 2019-10, Vol.224 (1), p.306-320
• Main Authors: Zheng, Tianhui, Sun, Juan, Zhou, Shirong, Chen, Saihua, Lu, Jian, Cui, Song, Tian, Yunlu, Zhang, Huan, Cai, Maohong, Zhu, Shanshan, Wu, Mingming, Wang, Yihua, Jiang, Ling, Zhai, Huqu, Wang, Haiyang, Wan, Jianmin
• Format: Article
• Language: English
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.16010

Rice ( Oryza sativa ) is a facultative short‐day ( SD ) plant, flowering early under SD and late under long‐day ( LD ) conditions. Ghd7 is a major regulator of flowering time in rice, which strongly delays flowering under LD . Induction of Ghd7 expression by phytochromes has been shown to contribute to photoperiodic regulation of flowering in rice. Here, we show that Ghd7 also is regulated by phytochromes at a post‐transcriptional level. We found that constitutive expression of Ghd7 delays flowering in the wild‐type (WT) background, but not in the se5 mutant background (deficient in functional phytochromes) under LD and that Ghd7 protein fails to accumulate in the se5 mutant. We also found that co‐expressing OsGIGANTEA ( Os GI ) with Ghd7 causes reduced accumulation of Ghd7 protein and partially suppresses the delayed flowering phenotype in the WT background, suggesting that phytochromes and Os GI play antagonist roles in regulating Ghd7 protein stability and flowering time. We show that Os PHYA , Os PHYB and Os GI could directly interact with Ghd7. Interestingly, Os PHYA and Os PHYB could inhibit the interaction between Os GI and Ghd7, thus helping to stabilize Ghd7 protein. Our results revealed a new level of Ghd7 regulation by phytochromes and Os GI in photoperiodic control of flowering in rice.